The use of polymeric sorbents is known in the area of analytical and preparative separations. The porous structure can be controlled by choice of monomers, amount of crosslinking copolymer, polymerization temperature, and the amount and type of porogenic solvent. These parameters and their affect on monolith pore structure are reviewed in detail in Okay, O. Prog. Polym. Sci. (2000) 25:711-779.
One commonly used polymeric monolith is formed from the free radical polymerization of styrene and divinylbenzene. Many examples of styrene/divinylbenzene polymers are known in the art, and have been applied in the areas of solid phase extraction and chromatography. For example, Premstaller, A. (2000) Anal. Chem. 72:4386 describes the performance of a monolithic chromatography bed comprising poly(styrene divinylbenzene) and compared it with a column packed with micropellicular poly(styrene divinylbenzene) polymer beads. A monolithic poly(styrene-divinylbenzene) was formed in capillary tubing and used to separate double stranded nucleic acids in preparation for electrospray ionization mass spectrometry. The monolithic column exhibited an improvement in column performance relative to a column packed with polymer beads.
Merhar, M. et al. (2002) Materiali in Tehnologije 36:163 describe a representative polymer monolithic disk and its use to separate a mixture of macromolecules (proteins).
US 2003/0229191 to Kallury describes a polymeric sorbent comprising a polymeric backbone adapted to facilitate one or more interactions selected from the groups consisting of a dipolar interaction and a hydrophobic interaction and an amide functionality associated with polymeric backbone and adapted to undergo one or more interactions selected from the group consisting of proton accepting, proton donating and dipolar interactions, and exhibiting a strong capacity for retention of polar molecules. The sorbent can be associated with supports including disks, membranes, and syringe barrel cartridges for sample pretreatment.
U.S. Pat. No. 5,616,407 to Fritz describes a functionalized macroporous poly(styrene divinylbenzene) particle comprising ionic functional groups for adsorbing analytes. Similarly, EP 0758261B1 and U.S. Pat. No. 5,618,438 to Fritz describe the use of the aforementioned macroporous poly(styrene divinylbenzene) particle in a solid phase extraction medium comprising a fibrous matrix and sorptive particles enmeshed in the matrix in a weight ratio of sorptive particles to fibrous matrix of 40:1 to 1:4. EP 498557A1 describes a method for preparing a solid phase extraction medium comprising a PTFE fibril matrix and sorptive particles enmeshed in said matrix and a method for isolating an analyte. The solid phase extraction medium is prepared by blending the particles with a PTFE emulsion and subjected to mixing to cause the fibrillation of the PTFE particles, and calendared to form a calendered sheet. The particles are described as being separate from each other and isolated in a PTFE fibril cage that restrains the particle.
U.S. Pat. No. 5,738,790 to Hagen describes a solid phase extraction medium comprising a porous nonwoven fibrous matrix comprising PTFE and blown microfibers and sorptive or reactive hydrophobic siliceous molecular sieve particles enmeshed in said matrix in a weight ration of 40:1 to 1:40.
Variations on the monomers that can be used in the preparation of polymeric sorbents have also been investigated. For example, EP 1159995 and U.S. Pat. No. 6,759,442 to Takahashi describe a packing material for solid phase extraction of hydrophobic and ionic substances, reportedly having hydrophobicity and an ion exchange group. The packing material is described as a particle obtained by copolymerizing a hydrophobic monomer (A) and a hydrophilic monomer (B) and introducing thereinto an ion exchange group, in which the ion exchange group is introduced allegedly without impairing the hydrophobic site.
U.S. Pat. No. 6,322,695 to Lee describes a porous resin comprising crosslinked polymer particles penetrated by channels for solid phase extraction. The polymeric particles are said to feature a hydrophobic component, at least one hydrophilic component and at least one ion exchange functional group. In certain embodiments, the hydrophobic monomer is divinylbenzene, the hydrophilic monomer is N-vinylpyrrolidone, and the copolymer is a sulfonated poly(divinylbenzene-co-N-vinylpyrrolidone).
U.S. Pat. No. 6,749,749 to Xie describes the preparation of permeable polymeric monolithic materials in column casings wherein the application of pressure allegedly avoids wall effects and swelling. In particular embodiments, filler materials such as polymer rods or silica beads are used as a framework for the polymer and allegedly provide greater mechanical strength.
Tsuda et al. in U.S. Pat. No. 6,723,157 and (2003) Analytical Sciences 20, 1061 describe the preparation of a type of fiber adsorbent having attached silica microparticles for adsorbing gaseous toluene at low concentrations. The silica microparticles are reportedly prepared by polymerizing silica oligomers under alkaline conditions and fixing them onto glass fibers, which were woven into a glass fiber. The surface of the silica microparticles was chemically modified by bonding C18 phases.
EP 0432438 describes molded adsorbents comprising a mixture of adsorbent particles, fine plastic particles and reinforcing fibers. The adsorbent is activated carbon, silica, alumina, or zeolites. U.S. Pat. No. 4,512,897 to Crowder describes a molecular separation column for effecting the differential distribution between two phases, the column containing a substantially homogenous solid stationary phase which comprises a porous matrix of fiber having particulate immobilized therein.
However, the polymeric sorbents described in the art are provided as particles which must be incorporated into a sorbent bed or enmeshed in fiber networks. The resultant articles are not convenient and inexpensive to manufacture, nor do they provide ease of use in solid phase extraction applications. The solid phase adsorption characteristics are limited, and the sorbents do not provide good retention of both polar and nonpolar analytes. In addition, the solid phase extraction media do not provide recovery of analytes in small eluant volumes with superior flow rates, allowing fast and efficient use of time, labor and solvents in analytical applications.